On December 10, 2021 12:28:56 PM GMT-03:00, German Gomez [off-list ref] wrote:

On 10/12/2021 13:38, Arnaldo Carvalho de Melo wrote:

quoted

Em Fri, Dec 10, 2021 at 02:47:49PM +0530, kajoljain escreveu:

quoted

On 12/1/21 6:03 PM, German Gomez wrote:

quoted

The size of the cache of register values is arch-dependant
(PERF_REGS_MAX). This has the potential of causing an out-of-bounds
access in the function "perf_reg_value" if the local architecture
contains less registers than the one the perf.data file was recorded on.

Since the maximum number of registers is bound by the bitmask "u64
cache_mask", and the size of the cache when running under x86 systems is
64 already, fix the size to 64 and add a range-check to the function
"perf_reg_value" to prevent out-of-bounds access.

Patch looks good to me.

Reviewed-by: Kajol Jain<redacted>

Thanks, applied.

- Arnaldo

Thanks Arnaldo, and the rest for the review.

I did send a v2 of this patch afterwards. The only difference was to
give credit to the reporter in the commit message with:

Reported-by: Alexandre Truong <redacted>

I'll add it.

- Arnaldo

Thanks,
German

quoted

quoted

Thanks,
Kajol Jain

quoted

Signed-off-by: German Gomez <redacted>
---
 tools/perf/util/event.h     | 5 ++++-
 tools/perf/util/perf_regs.c | 3 +++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
index 95ffed663..c59331eea 100644
--- a/tools/perf/util/event.h
+++ b/tools/perf/util/event.h

@@ -44,13 +44,16 @@ struct perf_event_attr;
 /* perf sample has 16 bits size limit */
 #define PERF_SAMPLE_MAX_SIZE (1 << 16)
 
+/* number of register is bound by the number of bits in regs_dump::mask (64) */
+#define PERF_SAMPLE_REGS_CACHE_SIZE (8 * sizeof(u64))
+
 struct regs_dump {
 	u64 abi;
 	u64 mask;
 	u64 *regs;
 
 	/* Cached values/mask filled by first register access. */
-	u64 cache_regs[PERF_REGS_MAX];
+	u64 cache_regs[PERF_SAMPLE_REGS_CACHE_SIZE];
 	u64 cache_mask;
 };
 

diff --git a/tools/perf/util/perf_regs.c b/tools/perf/util/perf_regs.c
index 5ee47ae15..06a7461ba 100644
--- a/tools/perf/util/perf_regs.c
+++ b/tools/perf/util/perf_regs.c

@@ -25,6 +25,9 @@ int perf_reg_value(u64 *valp, struct regs_dump *regs, int id)
 	int i, idx = 0;
 	u64 mask = regs->mask;
 
+	if ((u64)id >= PERF_SAMPLE_REGS_CACHE_SIZE)
+		return -EINVAL;
+
 	if (regs->cache_mask & (1ULL << id))
 		goto out;